The invention relates to an aqueous adhesive based on thermoplastic block copolymers. It is intended to contain only a small proportion of solvents. It can be used for the adhesive bonding of fibers or films.
Adhesives for bonding fibers are known. These can be reactive or non-reactive adhesives. Fibers of various kinds are known as fiber material. It is known, for example, that nonwoven substrates can be bonded to one another, or to plastic films, using adhesives. Such adhesive bonds are used, for example, in the manufacture of hygiene products. It is known that melt adhesives based on reactive polyurethanes can be used; liquid adhesives based on radiation-crosslinkable polymers are also known.
It is furthermore known that fibers can be adhesively bonded to yield high-strength fiber composites. In this context, fibers can be entirely incorporated into a polymer matrix. Polyurethanes or epoxy binding agents, for example, are known as a matrix material. EP 1161341 describes methods in which fibers in the form of fiber skeins or fiber fabrics are adhesively bonded to one another. A variety of polymers are listed as the adhesive, and solvent-containing adhesives, adhesive powders, adhesive dispersions are listed as the utilization form. For example, a powder made of a styrene block copolymer is used and bonded. This adhesive bond meets the requirements imposed in terms of adhesive strength and elasticity, so that these fibers can be connected to one another by pressing.
Powdered adhesives have the disadvantage, however, that they usually bond the fibers to one another only at single points. In addition, they must melt effectively in order to produce good adhesion to the surfaces. An alternative is to incorporate these adhesives into the melt. This, however, requires considerable equipment outlay for processing these melts. Damage to the substrate is, moreover, possible as a result of the high temperature.
Polymers are often manufactured in solvents. This enables appropriate synthesis, and adhesives manufactured therefrom are moreover easy to package and transport. In terms of their application, however, they have the disadvantage that considerable quantities of solvent are released. This is first of all critical from an environmental-engineering standpoint, and furthermore technical measures must also be taken to ensure industrial protection of employees. This requires considerable effort on the part of users. Organic solvents should therefore be decreased to the greatest extent possible in the context of adhesive bonding.
In addition, the styrene block copolymers that are often used are also not suitable for all purposes. These polymers are nonpolar. For a variety of fiber materials that optionally have an elevated number of polar groups, this can result in insufficient adhesion. It is possible for the fibers to be pretreated before processing, but these are additional, laborious working steps.